Think of it like a member of the Supreme Court preparing a decision. They don’t research every legal citation and every case. They have aides to do that,and to prepare briefs. But the decision, the ultimate responsibility for what the final document says, is with the justice. The same with a Papal Encyclical. They usually contain many references to prior encyclicals, councils, scripture and the writings of other Popes and Church Fathers. Those are researched for him, based on what the subject and purpose of the encyclical is. For example, the Pope may ask, “What did the early Church Fathers say about Divine Mercy?” He could also ask someone who has expertise in the topic to provide their (name removed by moderator)ut.
From that research, the Pope has others prepare “briefs” and discussion based on what he wants. Some of the language that is ultimately included in the encyclical may come from these papers and (name removed by moderator)ut from others, but as was stated in an earlier post, the final product is from the Pope and he is responsible for the message.
As a side note, any Pope should obviously have a strong familiarity in the items mentioned above, and he probably already knows what an early Church Father said or what an earlier Pope wrote on a subject he is interested in. And they most likely do some of their own reading and research, once the materials are gathered.
(Being a book person and a fan of musty old libraries, one of the few things I would ever ask for on this earth would be to spend a few hours in the Vatican Library).:heaven:
If you read encyclicals, it is often fairly easy to see the “style” of the Pope who wrote it, once you get past the formulaic stuff. They can be very enlightening and inspirational.